This Research Proposal seeks to elicit the mechanisms by which measles and influenza viruses predispose to secondary bacterial pneumonias. They emphasize the effects of these viruses on function of human PMNS. Normal PMNS infected in vitro and those from patients with measles or influenza infections will be studied in phagocytosis, adhesiveness, chemotaxis, radom migration and membrane deformability. By defining the functional compromise(s) rendered upon PMNS infected with measles or influenza viruses it is hoped that new insight will be gained into the management of the patient so infected with particular reference to the prevention of secondary bacterial pneumonias.